Glendalough, the valley of two lakes, has one of the most atmospheric monastic sites on Ireland. Established by St Kevin in the 6th century, the settlement was sacked time and again by the Vikings. But survived for over 600 years. The decline of the sites took place after the English forces razed the site in 1398. Pilgrims kept coming to this valley long time after that, in particular to celebrate St. Kevin. Most buildings and ruins date from 8th to 12 th century.